Extreme Heat
"Extreme heat occurs when summertime temperatures are much hotter or more humid than average" (Extreme Heat Resources and References for Providers). Extreme heat is particularly dangerous when occurring for a prolonged period (known as a “heat wave”). The National Weather Service (NWS) HeatRisk Tool provides information on project heat risk in an area over a 24 hour period. The tool incorporates how unusual the temperature is for the time of year, daytime and nighttime temperatures, and whether or not there is a high risk of heat-related health impacts.
Periods of extreme heat can cause serious illness, injury, or death to exposed populations. Extreme heat can make anyone sick, but some groups are at higher risk:
- individuals aged 65 and older
- individuals with chronic medical conditions
- pregnant people
- infants and children
- outdoor workers
- athletes
- people without access to air conditioning — which may include people experiencing homelessness and low-income households.
Extreme heat is also associated with increased demands for electricity and water, and can potentially stress local and regional infrastructure and services. Prolonged periods of extreme heat can have negative impacts on farming and livestock, and may lead to algae blooms that increase the risk of fish kills and contribute to degraded water quality. Extreme heat can also have a negative impact on health and productivity, with a direct impact on economic activity and travel. Warming temperatures and extreme heat have also been shown to have negative impacts on forests, aquatic ecosystems, and wildlife and fish populations (Rocky Mountain Forests).
Summertime temperatures are lower in the mountains and at higher elevations; therefore, extreme heat hazards in Colorado tend to occur in the Front Range, Grand Valley, Eastern Plains, and the Southwest (Colorado Natural Hazards Mitigation Plan). The number of extreme heat days in Colorado has been rising in recent years. In Denver, for instance, seven of the ten hottest years since 1874 occurred from 2000-2012 (NWS Boulder Denver). In Fort Collins, the number of days per year over 90 degrees from 2000-2013 was almost double the historic average (Extreme Heat). Past extreme heat events have caused damage to state and local infrastructure, especially roadways and utility networks. There are efforts across the state, at all levels, to reduce heat-related illness through increased access cooling, preparedness planning, and data collection.
Extreme heat can help create the conditions for drought and can exacerbate the impacts of drought by putting additional stress on available water supplies. Extreme heat can also lead to increased storm activity, which is linked to both high wind and flash flood hazards. It can also contribute to the spread of wildfires.
Air pollution spikes as temperatures rise. Two air pollutants of concern include ground-level ozone and particulate matter from wildfire smoke. Both air pollutants can harm human health. More research is needed to understand how heat-related illness is impacted by exposure to air pollution.
Colorado Enhanced State Hazard Mitigation Plan
The Colorado Enhanced Hazards Mitigation Plan is a key resource for an overview of extreme heat hazards and summaries of national and state-level data on extreme heat.
Colorado Enviroscreen
Colorado EnviroScreen helps identify areas in the state facing higher environmental and health burdens by analyzing various data. The five main categories of data include environmental exposures, environmental effects, climate vulnerability, sensitive populations (health indicators), and demographics.
Colorado Department of Public Health and Environment (CDPHE) Heat-Related Illness Dashboard
The Near Real-Time Heat-Related Illness Dashboard shows the rate of medical visits associated with heat-related illness (HRI) per 10,000 visits using data available through the National Syndromic Surveillance Program.
Guidance for Local Government Climate Adaptation
The Guidance for Local Government Climate Adaptation provides Colorado municipalities, counties, and special districts with over 25 implementable actions across five sectors. This resource was developed to help communities of all sizes—from rural towns to urban centers—take meaningful steps toward climate preparedness and adaptation.
National Weather Service
The National Weather Service is a key resource for the forecasting of extreme heat events and for the issuance of advisories and warnings.
National Oceanic and Atmospheric Administration (NOAA)
The National Oceanic and Atmospheric Administration’s National Climatic Data Center (NCDC) provides data on temperatures and extreme heat for the United States and for Colorado.
FEMA and Ready.Gov
FEMA and Ready.Gov have published useful guides for extreme heat preparation and response.